Process of manufacturing bifocal lenses.



No 848,335. PATENTED MAR. 26, 1907.

J. WIMMER. PROCESS OF MANUFACTURING BIPOGAL LENSES.

APPLICATION FILED NOV. 19, 1906.

4 v gi /1 2 i a WITNESSES:

' INVENTOR 9%% W BY ATTORNEY I UNITED STATES PATENT OFFICE.

JOHN WIMMER, oF' INDIANAPOLIS, INDIANA; THE INDIANA TRUST COMPANY EXEOUTOR 'OF SAID To all whom it may concern: Be it known that I, JOHN WIMMER, a citizen of the United States, residing at Indianapolis, in the county of Marion and State of Indiana, have invented certain new and useful Improvements in the Process of Manufacturing Bifocal Lenses, of which the following is a specification, reference being had therein to the accompanying drawings.

This invention relates to the art of manufacturing bifocal or multifocal integral lenses-i. e., integral lenses having a plurality of focal distances and composed of a larger lens having a lower index of refraction and one or more smaller lenses having a higher index of refraction united together. Throughout this specification the words major lens will be used to designate the larger part of the integral lens having the lower index of refraction and the words minor lens to d'esignatethe smaller part or parts of the integral lens having the higher index of refraction.

The object of this invention is to manufacture bifocal or multifocal lenses by uniting separatelpieces of glass having different indices of refraction into a single piece having the desired focal distances by means of a suitable flux or fusible cement which liquefies at a temperature below that of the fusing temperature of any of the pieces of glass of which the integral lens is composed. I attain thisobject by means of the process hereinafter described in the specification and illustrated in the accompanying drawings, in which similar numerals of reference designate like parts throughout the several views.

Figure 1 is a transverse sectional view of a major lens inwhich a depression. for receiving a minor lens is formed. Fig. 2 is a similar view showing my fusible powder placed in the depression thereof. Fig. 3 is a transverse sectional view of a minor lens prepared Specification of Letters Patent.

Application filed November 19. 1906. Serial No. 344,053.

-thereon, care being taken WIMMIER, DECEASED.

' PROCESS OF MANUEACTUFtING B IFOCAL LENSES.

Patented March 26, 1907.

.taken on the line A B of Fig. 8; and Fig. 8 is a front view of the same.

In order that others skilledin the art be en- I abl'ed to practice my invention of a process of manufacturing bifocal and multifocal lenses, I shall now. proceed to. describe the different steps of the same in detail, as follows: I- first procure a piece of, glass of a given index of refraction and of suitable dimensions from which to construct a major lens. I next grind or otherwise form in'such major lens a concave depression 2 of such a curvature as will fit the convex side of a minor lens of the Said depression is require-d focal distance. formed far enough to one side of the center of saidfmajor lens to leave the field or surface of the desired size. 3

. I select for a minor lens a piece of glass of a certain index of refraction differing from that 'of the major lens and that will make a minor lens 3 of the required focal distance and grind'or otherwise form and polish a convex surface4 on one of the sides of the same to correspond with and snugly fit the curvature of'the depression 2, wherein it is to be "placed. I next place the major and minor lenses 1 and 3 into a cleaning bath, which may be made, say, of pearlash and water,

111 the proportion, say, of one teaspoonful of nearlash to one pint of water, and heat this bath to the boiling-point and maintain it at thattemperature for a time silflicient not only to remove all grit and spots from the but also for the purpose of annealing or tempering them. The lenses are next removed ground and polished surfaces of the lenses, i

from said bath azzd thoroughly and carefully dried, taking care that all foreign matter is removed and nothing adheres to their surfaces. I next procure a supporting-block 5',

I which is composed of a heat-resisting material which 'also possesses the quality of retaining heat, and heat the same hot enough to thoroughly dry thelenses when placed not to heat said cold lenses when I next remove the block so hot as to cause Dlaced thereon to crack.

heated block 5 out of the furnace and place it upon a suitable bench conveniently situ-- ated relatively to the furnace. I next take the major-lens blank and carefully wipe the ICO polished surface of the de ression thereof and.

remove all traces of dust from said surface by a suitable blower or hand-bellows provided for that purpose, after which I place said lens-blank upon said heated block with the depression up. I next take the minor lens 3 and carefully wipe the convex surface thereof and remove the dust from said surface by means of the said blower or hand-bellows polished surfaces of the lenses-when heated sweat, and moisture forms on their surfaces. The-moisture is then wiped off of the surfaces of the lenses. The said blower is then applied to the convex surface of the minor and the conc'ave'surface of the major lenses to remove all dust or-moisture that may have collected or have been deposited on said surfaces. After the removal of all the moisture I next place a quantity of powdered glass flux, hereinafter described, into the depression 2, as shown in Fig. 2, and place said lens 1 and its supporting-block 5 in a furnace so arranged that the lens is shielded from the direct action of the heat during the time of heating. At about this time I place the minor lens 3 into another furnace and heat the same to about a tem perature e ual to that of the fusing-point of said. glass ux.

When the glass flux in the depression 2 of the major lens has boiled until it is clear, the minor lens 3, when properly heated, is removed from its furnace and placed with its convex side 4 into the depression 2 u on the boiling flux. I then procure a suita le iron rod, which is heated at one of its ends to about the same temperature as the minor lens, and apply it to said minor lens 3,'and the latter is pressed down into said depression and worked around therein until the greater portion of the now fluid glass flux and all the air-bubbles have been pressed out from between the surfaces of the concave depression of the major lens and convex surface 4 of the minor lens 3. For the purpose ofannealing the lens thus made it is now taken out of the furnace and placed in an annealing-oven, which should be of a temperature about equal to that of the lenses at the time they are taken out of the furnace; Said oven, with the lenses-therein, is caused to cool slowly until cooled to about the temperature of the outside atmosphere.

To complete the lens ready to be mounted, all that remains to be done is to grind the outside surfaces thereof to the required curvature and finally edge the lens preparatory. to fitting it to a frame.

A flux that may be used in this process of manufacturing bifocal or multifocal lenses may be made of flint-glass, powdered, sixteen parts; pearlash, six parts; common salt x two parts, and powdered borax, one part. These ingredients are mixed thoroughly together and placed in a crucible and reduced to the fluid state. The mixture thus fused is poured into a vessel containing water, the water drained off, and the. residue placed into a mortar and reduced to a fine powder. The flux or powder must be kept in a closed vessel to exclude the dust until required for use. n

An integral lens made by this method may be taken apart at any time without injury to the curves of the component parts thereof by subjecting the lens to sufficient heat to melt the flux which holds the parts together. This is very convenient where the minor lens is found to have been made so as to produce the wron focal distance.

BifocaI lenses have heretofore been made by the use of a cement, such as Canada balsam; but it was found thatlenses made in that way were unsatisfactory, because the component parts of the lens would come apart when the such heat and to jars as are incident to the ordinary use of eyeglasses.

- The component lenses manufactured by this method will not separate under any conditions of the ordinaryu'se' of spectacles or when exposed to any of the common accidents use of eyeglasses.

I claim v 1. k The process of manufacturing bifocal or multifocal integral lenses by formin in a larger piece of glass of a selected index of refraction a concave depression, and forming a convex surface on a smaller piece of glass having a different index of refraction, the radii of the curvature of the concave depression of the one and of the convex surface of .theother being the same and uniting them by then placing in said concave de ression a quantity of powdered-glass flux w ich fuses at a temperature below that required to make either of said pieces of glass flexible and subjecting the piece of glass with the powdered flux in its depression to sufficient heat to liquefy said flux and heating the other piece of glass to about the fusing temperature of said flux, and placin it with its convex surface down into the oiling fiux 'l in said concave depression and uniting the two pieces of glass by pressing the latter piece of glassinto said depression and working it around and about therein, so as to force out all of the air-bubbles and most of said flux from between the surfaces of said pieces of glass and then solidifying said flux by slowly cooling said blank lens.

2. The process of manufacturing bifocal or multifocal integral lenses by forming a piece of glass of a required index of refraction to a convex surface on one side of such a radius as to make a lens of the required focal distance and forming in parts of integral bifocal a lar er piece of glass ofa. .lower index of refraction than the first mensame was exposed to incident to the i tioned, a concavity of such a radiusas to fit the convex surface of the said first-mentioned piece of glass and uniting them by placing a powdered-glass flux, such as described, in such depression and heating said piece of glass, with the glass flux in its depression, suiliciently hot to melt said flux and then placing the convex surface of the first piece of glass on said melted flux and by pressing and working it around and about in said depression and thereby forcing the air and the greater portion of. said flux from between the surfaces of said pieces of glass, and leaving only'a very thin lihn of said flux between the surfaces of said pieces of glass and then solidifying said flux by slowly cooling said blank lens, and then grinding the surfaces of said lens to the desired form.

3. The recess of manufacturing bifocal or multifoca integral lenses by forming a piece of glass of a required index of refraction to a convex surface on one side of such aradius as to make a lens of the required focal distance and forming in a larger piece of glass of a lower index of refraction than the first mentioned, a concavity of such a radius as to fit the convex surface of the said first-mentioned the convex surface of the first piece of glass on said meltedfiux and bypr'essing and work ing it around and about 1n said depression and thereby forcing the air and the greater portion of said flux from between the surfaces of said iece of glass, and leaving only a very thin fi 111 of said flux betweenthe surfaces of said pieces of glass, and then slowlycooling the blank integral lens thus united by placing it in an oven heated to about the tern perature of the fused glass fluxand so constructed as to cool slowly and so arranged that its tem )erature is at all times under the control of t 1e operator, and then ermitting said even and its contents to s owly cool, thereby solidifying the said glass flux.

In testimony whereof I aflix my signature in presence of two witnesses.

' g JOHN WIMMER. I Witnesses:

THOMPSON R. BELL, Miss E. THoMPso-N. 

